Association of Prehospital Rearrest With Outcome Following Out-of-Hospital Cardiac Arrest: A Systematic Review and Meta-Analysis of Observational Studies.

OBJECTIVES: Exposure to prehospital rearrest has previously been associated with mortality following out-of-hospital cardiac arrest (OHCA). Our objective was to conduct a systematic review and meta-analysis examining the association between prehospital rearrest and survival in adults following OHCA resuscitation. METHODS: We searched the PubMed, Scopus, and Web of Science bibliographic databases for observational studies that included adult OHCA patients who achieved return of spontaneous circulation in the prehospital setting following OHCA and reported survival to hospital discharge data stratified by rearrest status. The primary exposure was prehospital rearrest. The primary outcome for this study was survival to hospital discharge. Secondary outcomes included survival with a favorable neurological outcome and rearrest prevalence. We pooled data using inverse heterogeneity modeling and presented effect sizes for the survival outcomes as odds ratios with 95% confidence intervals. We quantified heterogeneity using Cochran's Q and the I2 statistic and examined small study effects using Doi plots and the LFK index. RESULTS: Of the 84 publications screened, we included 7 observational studies containing 27,045 patients with survival to hospital discharge data. Rearrest was common (30% [18-43%]; n = 7 studies; Q = 1086.1, p < 0.001; I2 = 99%; LFK index = 1.21) and associated with both decreased odds of survival to discharge (pooled aOR: 0.27 [0.22, 0.33]; n = 7 studies; Q = 32.2, p < 0.01, I2 = 81%, LFK index = -0.08) and decreased odds of survival to discharge with a favorable neurological outcome (pooled aOR: 0.25, [0.22, 0.28]; n = 4 studies; Q = 3.5, p = 0.3; I2 = 13%, LFK index = 1.30). CONCLUSIONS: Rearrest is common and associated with decreased survival following OHCA. The pooled result of this meta-analysis suggests that preventing rearrest in five patients would be necessary to save one life.

Tumor cell-derived spermidine promotes a pro-tumorigenic immune microenvironment in glioblastoma via CD8+ T cell inhibition.

The glioblastoma microenvironment is enriched in immunosuppressive factors that potently interfere with the function of cytotoxic T lymphocytes. Cancer cells can directly impact the immune system, but the mechanisms driving these interactions are not completely clear. Here we demonstrate that the polyamine metabolite spermidine is elevated in the glioblastoma tumor microenvironment. Exogenous administration of spermidine drives tumor aggressiveness in an immune-dependent manner in pre-clinical mouse models via reduction of CD8+ T cell frequency and phenotype. Knockdown of ornithine decarboxylase, the rate-limiting enzyme in spermidine synthesis, did not impact cancer cell growth in vitro but did result in extended survival. Furthermore, glioblastoma patients with a more favorable outcome had a significant reduction in spermidine compared to patients with a poor prognosis. Our results demonstrate that spermidine functions as a cancer cell-derived metabolite that drives tumor progression by reducing CD8+T cell number and function.

GAP43-dependent mitochondria transfer from astrocytes enhances glioblastoma tumorigenicity.

The transfer of intact mitochondria between heterogeneous cell types has been confirmed in various settings, including cancer. However, the functional implications of mitochondria transfer on tumor biology are poorly understood. Here we show that mitochondria transfer is a prevalent phenomenon in glioblastoma (GBM), the most frequent and malignant primary brain tumor. We identified horizontal mitochondria transfer from astrocytes as a mechanism that enhances tumorigenesis in GBM. This transfer is dependent on network-forming intercellular connections between GBM cells and astrocytes, which are facilitated by growth-associated protein 43 (GAP43), a protein involved in neuron axon regeneration and astrocyte reactivity. The acquisition of astrocyte mitochondria drives an increase in mitochondrial respiration and upregulation of metabolic pathways linked to proliferation and tumorigenicity. Functionally, uptake of astrocyte mitochondria promotes cell cycle progression to proliferative G2/M phases and enhances self-renewal and tumorigenicity of GBM. Collectively, our findings reveal a host-tumor interaction that drives proliferation and self-renewal of cancer cells, providing opportunities for therapeutic development.

Measuring the Effect of Audio Instructions on the Time and Effectiveness of Tourniquet Application by Laypeople.

OBJECTIVE: The "Stop the Bleed" campaign was created to educate laypeople about bleeding control and make bleeding control kits available in public locations. Unfortunately, previous research has indicated that up to half of all laypeople cannot effectively apply a tourniquet. The purpose of this study was to determine if laypeople could apply tourniquets more effectively with just-in-time training using combined audio-written instructions versus written-only instructions. METHODS: We conducted a prospective randomized study comparing the application of a tourniquet using a simulated bleeding arm. Participants were laypeople 18 years and older and excluded those with any previous tourniquet experience or training. Participants were randomized to just-in-time training using either audio-written or written-only instructions. Time in seconds to tourniquet application and the effectiveness of the tourniquet application was recorded. Effective application was defined as stopping the flow or significantly slowing the flow to a slow drip. Ineffective tourniquet placement was defined as not significantly changing the flow. Statistical analysis was performed using Fisher's exact, t-test, and linear regression. RESULTS: Eighty-two participants were included; 40 were in the audio-written instructions group, and 58.5% were male. The audio-written group's effective application rate was 92.5% and that of the written-only group was 76.2%. A significantly higher rate of ineffective tourniquet application was noted for the written-only group (23.8%), versus the audio-written group (7.5%), p = .04. Regardless of the type of instructions used, time to effective application of the tourniquet decreased as participant age increased (p = 0.02, 95%CI (-1.24, -0.13). There was no relationship between age and effective tourniquet application (p = 0.06). Time for tourniquet placement was not different between the audio-written (mean 100.4 seconds) and written-only (mean 106.1 seconds) groups (p = 0.58). CONCLUSION: This study suggests that combined audio-written instructions decrease the rate of ineffective tourniquet application by laypeople compared with written-only instructions. Further studies are needed to assess if audio instructions and just-in-time training can further maximize effective tourniquet application.

Tracheal Transection From Gunshot Wound to the Neck.

A male patient presented with a gunshot wound superior to his left scapula and difficulty breathing. En route to the emergency department, he rapidly became unresponsive, culminating in a cricothyroidotomy by paramedics. Oxygen saturation was 70% on arrival, and a tracheobronchial injury was suspected. In the operating room, a complete transection of the mid trachea was found and repaired. Postoperatively, the patient had acute respiratory distress syndrome. He was placed on extracorporeal membrane oxygenation and was eventually decannulated on postoperative day 12. The need for immediate identification of airway inadequacy, despite appropriate interventions, is underscored by this case report.

Membrane Distribution and Activity of a Neuronal Voltage-Gated K+ Channel is Modified by Replacement of Complex Type N-Glycans with Hybrid Type.

Abnormal modifications in N-glycosylation processing are commonly associated with neurological disorders, although the impact of specific N-glycans on neuronal excitability is unknown. By replacement of complex types of N-glycans with hybrid types in neuroblastoma cells, we provide the first study that addresses how distinct N-glycan types impact neuronal excitability. Using CRISPR/Cas9 technology, NB_1, a clonal cell line derived from rat neuroblastoma cells (NB), was modified to create an N-glycosylation mutant cell line, NB_1 (-Mgat2), which expresses predominantly hybrid type N-glycans. Western and lectin blotting, flow cytometry, TIRF and DIC microscopy, and patch clamp studies were conducted. Lectin binding revealed the predominant type of N-glycans expressed in NB_1 (-Mgat2) is hybrid while those of NB and NB_1 are complex. Kv3.1 b-expressing cells with complex N-glycans localized more glycosylated Kv3.1b to the neurites than cells with hybrid N-glycans. Further the absence of N-glycan attachment to Kv3.1b was critical for sub-plasma distribution of Kv3.1b to neurites in primary adult mammalian neurons, along with NB cells. Replacement of complex type N-glycans with hybrid type hindered the opening and closing rates of outward ionic currents of Kv3.1 b-expressing NB cells. The lacks of N-glycan attachment hindered the rates even more but were not significantly different between the NB cell lines. Taken together, our evidence supports N-glycosylation impacts the sub-plasma membrane localization and activity of Kv3.1 b-containing channels. We propose that N-glycosylation processing of Kv3.1 b-containing channels contributes to neuronal excitability, and abnormal modifications in N-glycosylation processing of Kv3.1b could contribute to neurological diseases.

Predominant Expression of Hybrid N-Glycans Has Distinct Cellular Roles Relative to Complex and Oligomannose N-Glycans.

Glycosylation modulates growth, maintenance, and stress signaling processes. Consequently, altered N-glycosylation is associated with reduced fitness and disease. Therefore, expanding our understanding of N-glycans in altering biological processes is of utmost interest. Herein, clustered regularly interspaced short palindromic repeats/caspase9 (CRISPR/Cas9) technology was employed to engineer a glycosylation mutant Chinese Hamster Ovary (CHO) cell line, K16, which expresses predominantly hybrid type N-glycans. This newly engineered cell line enabled us to compare N-glycan effects on cellular properties of hybrid type N-glycans, to the well-established Pro(-)5 and Lec1 cell lines, which express complex and oligomannose types of N-glycans, respectively. Lectin binding studies revealed the predominant N-glycan expressed in K16 is hybrid type. Cell dissociation and migration assays demonstrated the greatest strength of cell-cell adhesion and fastest migratory rates for oligomannose N-glycans, and these properties decreased as oligomannose type were converted to hybrid type, and further decreased upon conversion to complex type. Next, we examined the roles of three general types of N-glycans on ectopic expression of E-cadherin, a cell-cell adhesion protein. Microscopy revealed more functional E-cadherin at the cell-cell border when N-glycans were oligomannose and these levels decreased as the oligomannose N-glycans were processed to hybrid and then to complex. Thus, we provide evidence that all three general types of N-glycans impact plasma membrane architecture and cellular properties.

Cell surface N-glycans influence the level of functional E-cadherin at the cell-cell border.

E-cadherin is crucial for adhesion of cells to each other and thereby development and maintenance of tissue. While it is has been established that N-glycans inside the cell impact the level of E-cadherin at the cell surface of epithelial-derived cells, it is unclear whether N-glycans outside the cell control the clustering of E-cadherin at the cell-cell border. Here, we demonstrate reduction of N-glycans at the cell surface weakened the recruitment and retention of E-cadherin at the cell-cell border, and consequently reduced the strength of cell-cell interactions. We conclude that N-glycans at the cell surface are tightly linked to the placement of E-cadherin at the cell-cell border and thereby control E-cadherin mediated cell-cell adhesion.